Voting Used to Protect Qubits

Someday quantum computers may be used for some advanced calculations electronics computers cannot perform efficiently. One issue plaguing the development of quantum computers however is decoherence, which causes quantum information to be lost. Researchers at the University of Southern California however have recently developed a technique to correct errors caused by decoherence, resulting in a five-fold increase in probability of receiving a correct answer.

For this research, a D-Wave Two quantum processor was used. While it is not a true quantum computer, it is one of the first available quantum processors, capable of running some quantum algorithms, and is also susceptible to decoherence. In a quantum device, information is stored in qubits, which are particles in superposition, and that is a quantum mechanical phenomenon in which a particle can exist in multi-exclusive states at the same time. Decoherence is when the superposition collapses down to a single state, causing information to be lost. What the researchers have done is encoded qubits in larger blocks that can be decoded by a majority vote. If one qubit in the block suffers decoherence, the other two can out vote it. The blocks are also then connected to a fourth qubit, which makes the system too large to easily suffer decoherence.

If we are ever to see quantum computing become a reality, rigorous error correction will be needed, and this is at least a step towards that.